1. Field of the Invention
The invention is related to an improved device of the disk transmission unit for an electromotive bicycle with particular reference to how the transmission device is rotated idly and reduce noises.
2. Description of the Prior Art
The so call bicycle in the present invention include a double wheel bicycle, and any bike which has at least double wheels that is directly driven by electric power.
The difference between the disk transmission unit of an electromotive bicycle and car, or motorcycle, or other vehicle is that an electromagnetic field is formed between the stator and rotor. A current is supplied by a battery to rotate the rotor. The related prior art may refer to U. S. Pat. Nos. 5,164,623, 5,450,915, 5,272,938, 4,490,637, 3,095,516, 4,021,690, and U.S. Pat. No. 3,792,742.
Since the initial rotary speed of the rotor is not suitable for driving the wheels directly and in order to increase the torque of the output electromagnetic field, in general, a deceleration gear must be used to reduce speed and increase torque.
The prior art transmission unit of the disk motor of an electromotive bicycle will generate large noises, especially, in the case that the stator is installed on the wheel axis to drive the wheel frame.
When the power is fed into the prior-art transmission device, the inner ring gear is driven by an main gear through a planet gear, and the spoke fixing the inner ring gear is rotated therefor. As the current is interrupted, the spoke will rotate continuously by the inertial force, thus the inner ring gear will rotate. Although in the prior art device, an unidirectional clutch is installed between a deceleration gear set and an active gear, the planetary gear and inner ring gear on the periphery thereof is possible to prevent the free rotation of the spoke.